The integration of an LDMOS with silicon-germanium (SiGe) technology has gained attention for power management and automotive applications. The LDMOS device is used in a RF/microwave power amplifier. The LDMOS is fabricated on a silicon substrate or on a silicon-on-insulator (SOI) substrate. Such a silicon-based FET is widely used in power management and power amplifiers where high voltage input and output are required and regulated. The integration of an LDMOS with silicon-germanium (SiGe) technology is an evolved semiconductor technology that integrates two formerly separate semiconductor technologies, the silicon-germanium (SiGe) BiCMOS technology and the high voltage CMOS transistor—in a single integrated circuit.
A traditional LDMOS (laterally diffused metal oxide semiconductor) device usually uses a horizontal drift region between a drain region and a gate region to drop high voltage which causes the LDMOS device to burn out. When the voltage drop goes as high as 120V and higher, the length of the drift region is typically required longer than 6 μm. Such a long drift region occupies a huge area in the LDMOS device. Also, in the traditional LDMOS process, the drift region doping is doped uniformly across the region laterally and is sometimes shared with well doping; therefore, it is difficult to independently tune the electrical field laterally for the purpose of achieving the best performance of both blocking voltage and on-resistance.